A typical wireless communication system comprises a plurality of nodes, each performing a specific task. Among other types of nodes in GSM system architecture. the system comprises at least one MSC (Mobile Switching Center) in communication with at least one HLR (Home Location Register), an OSS (Operation Support System) and a plurality of BSS (Base Stations Systems) serving as access points for MS (mobile stations). A BSS comprises a BSC (Base Station Controller) and one or more BTSs (Base Transceiver Stations). The BSC is responsible for the exchange of messages between a MSC (Mobile Switching Center) and a BTS. Traffic and signaling transferred between a MSC and a MS (Mobile Station) will usually pass transparently through a BSC. The BSC, which is a functional entity within GSM architecture, is responsible for RR (Radio Resource) allocation to a MS, frequency administration and handover between BTSs controlled by the BSC. Radio interfaces are terminated at a Base Transceiver Station. Each BTS may comprise: a number of TRXs (Transceivers), typically between 1 and 16; base band processing means; Combiners; radio equipment; and antennas. In GSM systems the BTS is also responsible for ciphering of an air interface.
The MSC is a switching entity of the wireless communications system that is responsible for establishing and controlling communications between subscribers. The HLR is a database found within wireless communication systems, which stores subscriber data relating to services and features in addition to location area based information. The OSS (Operations Support System) is a network management system supporting specific management functions, such as fault, performance, statistical analysis, security, configuration etc.
Unbalance between different parts of an antenna system will degrade cell performance. A cell may have BCCH (Broadcast Control Channel) coverage but not TCH (traffic Channel) or SDCCH (Stand-alone dedicated channel) coverage which will result in TCH and/or SDCCH drops. A broadcast channel is a common channel transmitting to an entire cell area of a base transceiver station, in order to provide cell information for mobile stations located in the cell. In GSM, a broadcast channel includes a FCCH (frequency correction channel), a SCH (synchronization channel) and a BCCH (broadcast control channel). The BCCH channel contains specific parameters needed by a mobile in order that it can identify a network and gain access to it. Typical information included is a LAC (Location Area Code) and a RAC (Routing Area Code), a MNC (Mobile Network Code) and a BA (BCCH Allocation) list. The SDCCH channel is used in GSM systems to provide a reliable connection for signaling and SMS (Short Message Service) messages.
The unbalance mentioned above can be hard to locate as it can be due to wear and tear or malfunctions of any parts (TRX, feeders, antennas etc) within the base station system. A BCCH TRX (transceiver) is transmitting all the time, for example this will cause higher wear and tear on the BCCH TRX compared to other TRXs in a cell. Cellular operators are in need of a simple and fast implementation for regularly monitoring both state and performance of each antenna and BSS transceiver. Radio transmission faults regularly occur and in many cases poor speech quality, poor system access, and poor reliability are due to transceiver malfunctions, broken feeders, malfunctioning and/or wrongly directed antennas not covering a planned coverage areas etc.
The industry has provided various methods for monitoring the state of a BSS, particularly the state of BSS transceivers which are directly responsible for radio communication between a network and mobile subscribers. Periodic transmission of status information of transceivers sent from a BSS to a MSC is one of the most common methods. The MSC forwards the status information data to an Operation Support System (OSS) where it is stored in a database. Then, periodically, this data is manually checked and verified by network administrators. When an error or a problem is detected or suspected in a BSS, technicians are in most cases sent in order to fix the problem. In many cases, the technicians are working for another company and such a problem solving procedure might take a lot of valuable time. In some cases the technicians have performed a wrong installation of feeders or antennas and in some cases it is difficult to detect if the problem is arising from feeders, transceivers or antennas.